Some sim racing games have been offered as offline games; for example the SBK superbike games by Milestone, the games by Brazilian developer Reiza Studios (Stock Car Extreme, Formula Truck), and much of Sector3's content can be bought on disc, incluing their old Simbin stuff.
There's also the numerous Richard Burns Rally mods, some of which are superior to Dirt Rally in my opinion.
Bigger games, like Dirt Rally, Codemasters F1, Assetto Corsa, and Project Cars will never appear on GOG. I can't see it.
tinyE: Anyone here ever play the original DIRT?
Yes, it's my favourite in the Dirt series. Dirt Rally is really good as well but lacks the variety of the other Dirt games. On the other hand the physics in Dirt Rally is more challenging ,,, and thus more interesting in some ways. They appeal to two very different types of gamers though, where the Dirt games were aimed at a much broader audience than Dirt Rally is.